Despite all that has been said about the dreadful death of Daniel Pelka, we seem little wiser about how abused children become "invisible" to professionals. The serious case review into his death subscribes to the increasingly popular explanation that professionals miss the obvious because they are too "optimistic". The "rule of optimism" is said to have resulted in professionals naively and hopefully believing what Daniel's parents told them, and denying what was in front of them.

Over the past year, I have been observing social workers in their encounters with children and parents. The aim was to document how they work with parents and what enables, or stops, interventions from being effective. In the majority of cases, children were seen and assessments made of their safety, but, in a minority, children did become invisible.

On one home visit, the social worker, faced by an angry mother denying child neglect, completely ignored the two children who were right in front of her. Another social worker failed to challenge a belligerent father about the neglect she had found, and did not see the children – aged 10 and 14 – on their own. Afterwards, she spoke vividly about how she felt the neglected house – especially the smell – overcame her. Neither social worker believed a word the parents said.

Far from being optimistic, the social worker's state of mind was closer to helplessness. These were not bad or psychologically flawed practitioners; they were outmanoeuvred by aggressive parents, and overcome by the suffering and sadness in the atmosphere of such homes and in children's lives. The case review on Daniel refers to how his home "was clearly one with a tense and sometimes violent atmosphere". Caught up in such atmospheres, social workers become overwhelmed by anxiety and lose their purpose and focus.

Teachers, who tend not to visit the home, can be immobilised by how parents project into them their rage, lies and irrational beliefs – such as Daniel's supposed eating "obsession".

The case review concludes that Daniel "must have felt utterly alone and worthless … At times he was treated as inhuman, and the level of helplessness he must have felt in such a terrifying environment would have been overwhelming." Perhaps the most painful truth that must be confronted is that, faced with the helplessness of children, social workers themselves can become helpless because they find the children's suffering unbearable.

Another reason a minority of children became invisible was because social workers had so little time available.

Daniel's case review shows that three of the four social work assessments were superficial. It refers to how the social work submission to the review spoke of "the heavy workload that [social workers] were experiencing at this time and that there were 'high levels of bureaucracy' … which was said to reduce their time on effective practice interventions".

In my study, those working conditions led to assessments being made after a matter of minutes spent alone with children. Social workers were painfully aware of the limits of their helpfulness. They feared they could not achieve the depth of relationship that children such as Daniel need if they are to disclose their abuse.

The government needs to recognise and counter this helplessness by providing the staffing and organisational conditions that enable the children's workforce, including social workers, teachers, doctors and the police, to spend quality time with children and receive the kind of emotionally aware supervision and support that is essential to being child-centred and helpful.